Slobodanka Stojkovic | RMIT University (original) (raw)
Papers by Slobodanka Stojkovic
CO2 -concentrating mechanisms in three southern hemisphere strains of Emiliania huxleyi
Journal of phycology, 2013
Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence... more Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence the way phytoplankton acquire inorganic carbon. All phytoplankton rely on ribulose-bisphosphate carboxylase oxygenase (RUBISCO) for assimilation of inorganic carbon in photosynthesis, but this enzyme is inefficient at present day CO2 levels. Many algae have developed a range of energy demanding mechanisms, referred to as carbon concentrating mechanisms (CCMs), which increase the efficiency of carbon acquisition. We investigated CCM activity in three southern hemisphere strains of the coccolithophorid Emiliania huxleyi W. W. Hay & H. P. Mohler. Both calcifying and non-calcifying strains showed strong CCM activity, with HCO3 (-) as a preferred source of photosynthetic carbon in the non-calcifying strain, but a higher preference for CO2 in the calcifying strains. All three strains were characterized by the presence of pyrenoids, external carbonic anhydrase (CA) and high affinity for CO2 in...
Photosynthetic characteristics of two Cylindrospermopsis raciborskii strains differing in their toxicity
Journal of phycology, 2014
We studied the growth and photosynthetic characteristics of a toxic (CS506) and a nontoxic strain... more We studied the growth and photosynthetic characteristics of a toxic (CS506) and a nontoxic strain (CS509) of the bloom-forming cyanobacterium Cylindrospermopsis raciborskii grown under identical experimental conditions. When exposed to light-saturating growth conditions (100 μmol photons · m(-2) · s(-1) ), values for maximal photosynthetic capacity (Pmax ) and maximum quantum yield (Fv /Fm ) indicated that both strains had an equal ability to process captured photons and deliver them to PSII reaction centers. However, CS506 grew faster than CS509. This was consistent with its higher light requirement for saturation of photosynthesis (Ik ). Greater shade tolerance of CS509 was indicated by its higher ability to harvest light (α), lower photosynthetic light compensation point (Ic ), and higher chlorophyll a to biovolume ratio. Strain-specific differences were found in relation to non-photochemical quenching, effective absorption cross-sectional area of PSIIα-centers (σPSIIα), and the...
Nutrient induced fluorescence transients (NIFTs) provide a rapid measure of P and C (co-)limitation in a green alga
European Journal of Phycology, 2015
Harmful Algae, 2015
Cylindrospermopsis raciborskii is a toxic cyanobacterium which is responsible for the formation o... more Cylindrospermopsis raciborskii is a toxic cyanobacterium which is responsible for the formation of Harmful Algal Blooms (HABs) and it is commonly described to prefer low light conditions. To elucidate the mechanisms that makes this species successful in such environments, we studied the physiological characteristics of C. raciborskii (strain NPD) exposed to both saturating (80 mmol photons m À2 s À1 ) and suboptimal (10 mmol photons m À2 s À1 ) light intensities. When exposed to the low light of 10 mmol photons m À2 s À1 , C. raciborskii showed a slower cell division rate (m c ), lower respiration rate (R d ) and higher cell quotas of Chl a and phycocyanin. However, no differences in the cellular light harvesting efficiency (a) and maximal photosynthetic rate (P max ) were observed. Under low light, the unchanged photosynthesis was associated with both functional maintenance of the photosynthetic machinery and a larger cross-sectional area of PSIIa-centres (sPSIIa). In relation to the literature, our results indicate that C. raciborskii NPD responds to low light by changing the size of the light harvesting antenna. Ecologically, the physiological acclimations observed suggest that C. raciborskii NPD can perform well in environments where light intensity is low and relatively stable, as might occur during the final stages of HABs. ß
Photosynthesis research, 2014
The extremophilic green microalga Chlamydomonas acidophila grows in very acidic waters (pH 2.3-3.... more The extremophilic green microalga Chlamydomonas acidophila grows in very acidic waters (pH 2.3-3.4), where CO2 is the sole inorganic carbon source. Previous work has revealed that the species can accumulate inorganic carbon (Ci) and exhibits high affinity CO2 utilization under low-CO2 (air-equilibrium) conditions, similar to organisms with an active CO2 concentrating mechanism (CCM), whereas both processes are down-regulated under high CO2 (4.5 % CO2) conditions. Responses of this species to phosphorus (Pi)-limited conditions suggested a contrasting regulation of the CCM characteristics. Therefore, we measured external carbonic anhydrase (CAext) activities and protein expression (CAH1), the internal pH, Ci accumulation, and CO2-utilization in cells adapted to high or low CO2 under Pi-replete and Pi-limited conditions. Results reveal that C. acidophila expressed CAext activity and expressed a protein cross-reacting with CAH1 (the CAext from Chlamydomonas reinhardtii). Although the fu...
High CO2, UV, and carbon partitioning in Thalassiosira pseudonana
The interactive effects of uv radiation and enhanced CO2 concentrations on aquatic photoautotrophs
Understanding the effects of global climate change on the algae that form the basis of most aquat... more Understanding the effects of global climate change on the algae that form the basis of most aquatic food chains is of paramount importance in our ability to make informed decisions about the future of production systems, marine ecosystems, and the global carbon cycle. Despite the Montreal Protocol to restrict the release of harmful chlorofluorocarbons into the atmosphere, ozone levels have not recovered at all latitudes, and in some regions levels of UVB are still rising due to interactions with phenomena related to climate change. However, the effects of UV radiation may be modulated by other environmental changes. In this review, we discuss how factors such as elevated CO 2 and ocean acidification, increasing temperature, and reduced nutrient supply associated with enhanced stratification can interact with UV radiation to affect algal physiological performance and growth. For instance, nutrient limitation enhances UV-induced inhibition due to the reduced capacity of algae to screen out UVB and/or impairment of their capacity to repair damage. Higher temperatures tend to promote repair more than photochemical damage so result in a net reduction of UV inhibition. Elevated CO 2 and ocean acidification has complex interactions with UV radiation, with mixed net outcomes for algal productivity. Differential effects of UVA and UVB have been shown to depend on their irradiance levels; while moderate levels of UVA stimulate growth and photosynthesis of some algae, UVB almost always results in harm to marine primary producers.
Photosynthetic characteristics of two Cylindrospermopsis raciborskii strains differing in their toxicity
Marine microbes in the Plastic Age
Microbiology Australia, 2014
ABSTRACT We are living in the ‘Plastic Age’, but unfortunately our non-human relatives with whom ... more ABSTRACT We are living in the ‘Plastic Age’, but unfortunately our non-human relatives with whom we share our planet are not adapted to cope with the thousands of tons of plastic waste entering rivers, seas and oceans each year. Plastic poses both physical and chemical threats to aquatic life. It leads to damage or death of animals following plastic entanglement or ingestion and/or can lead to bioaccumulation of co-pollutants absorbed on plastic surfaces. Once ingested, co-pollutants can be absorbed into tissues and accumulated in the food chain. As nature’s biodegraders and recyclers, microorganisms may play a role in mitigating the impact of our disposable plastic lifestyle, or alternatively, plastic may serve as a vector for transport of pathogenic microorganisms into marine fauna. Here, we review current understanding of the microbiology of marine plastics and highlight future challenges for this emerging research discipline.
Phycologia, 2013
2013. Impacts of nitrogen limitation on the sinking rate of the coccolithophorid Emiliania huxley... more 2013. Impacts of nitrogen limitation on the sinking rate of the coccolithophorid Emiliania huxleyi (Prymnesiophyceae). Phycologia 52: 288-294.
Journal of Plant Physiology, 2014
We studied the physiological acclimation of growth, photosynthesis and CO 2 -concentrating mechan... more We studied the physiological acclimation of growth, photosynthesis and CO 2 -concentrating mechanism (CCM) in Cylindrospermopsis raciborskii exposed to low (present day; L-CO 2 ) and high (1300 ppm; H-CO 2 ) pCO 2 . Results showed that under H-CO 2 the cell specific division rate ( c ) was higher and the CO 2and light-saturated photosynthetic rates (V max and P max ) doubled. The cells' photosynthetic affinity for CO 2 (K 0.5 CO 2 ) was halved compared to L-CO 2 cultures. However, no significant differences were found in dark respiration rates (R d ), pigment composition and light harvesting efficiency (˛). In H-CO 2 cells, non-photochemical quenching (NPQ), associated with state transitions of the electron transport chain (ETC), was negligible. Simultaneously, a reorganisation of PSII features including antenna connectivity (J con PSII␣), heterogeneity (PSII␣/) and effective absorption cross sectional area (PSII␣/) was observed. In relation to different activities of the CCM, our findings suggest that for cells grown under H-CO 2 : (1) there is down-regulation of CCM activity; (2) the ability of cells to use the harvested light energy is altered; (3) the occurrence of state transitions is likely to be associated with changes of electron flow (cyclic vs linear) through the ETC; (4) changes in PSII characteristics are important in regulating state transitions.
CO 2 -concentrating mechanisms in three southern hemisphere strains of Emiliania huxleyi
Journal of Phycology, 2013
Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence... more Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence the way phytoplankton acquire inorganic carbon. All phytoplankton rely on ribulose-bisphosphate carboxylase oxygenase (RUBISCO) for assimilation of inorganic carbon in photosynthesis, but this enzyme is inefficient at present day CO2 levels. Many algae have developed a range of energy demanding mechanisms, referred to as carbon concentrating mechanisms (CCMs), which increase the efficiency of carbon acquisition. We investigated CCM activity in three southern hemisphere strains of the coccolithophorid Emiliania huxleyi W. W. Hay & H. P. Mohler. Both calcifying and non-calcifying strains showed strong CCM activity, with HCO3 (-) as a preferred source of photosynthetic carbon in the non-calcifying strain, but a higher preference for CO2 in the calcifying strains. All three strains were characterized by the presence of pyrenoids, external carbonic anhydrase (CA) and high affinity for CO2 in photosynthesis, indicative of active CCMs. We postulate that under higher CO2 levels cocco-lithophorids will be able to down-regulate their CCMs, and re-direct some of the metabolic energy to processes such as calcification. Due to the expected rise in CO2 levels, photosynthesis in calcifying strains is expected to benefit most, due to their use of CO2 for carbon uptake. The non-calcifying strain, on the other hand, will experience only a 10% increase in HCO3 (-) , thus making it less responsive to changes in carbonate chemistry of water.
Photosynthetic characteristics of two Cylindrospermopsis raciborskii strains differing in their toxicity
Journal of Phycology, 2014
We studied the growth and photosynthetic characteristics of a toxic (CS506) and a nontoxic strain... more We studied the growth and photosynthetic characteristics of a toxic (CS506) and a nontoxic strain (CS509) of the bloom-forming cyanobacterium Cylindrospermopsis raciborskii grown under identical experimental conditions. When exposed to light-saturating growth conditions (100 μmol photons · m(-2) · s(-1) ), values for maximal photosynthetic capacity (Pmax ) and maximum quantum yield (Fv /Fm ) indicated that both strains had an equal ability to process captured photons and deliver them to PSII reaction centers. However, CS506 grew faster than CS509. This was consistent with its higher light requirement for saturation of photosynthesis (Ik ). Greater shade tolerance of CS509 was indicated by its higher ability to harvest light (α), lower photosynthetic light compensation point (Ic ), and higher chlorophyll a to biovolume ratio. Strain-specific differences were found in relation to non-photochemical quenching, effective absorption cross-sectional area of PSIIα-centers (σPSIIα), and the antenna connectivity parameter of PSIIα (Jcon PSIIα). These findings highlighted differences in the transfer of excitation from phycobilisome/PSII to PSI, on the dependence on different pigments for light harvesting and on the functioning of the PSII reaction centers between the two strains. The results of this study showed that both performance and composition of the photosynthetic apparatus are different between these strains, though with only two strains examined we cannot attribute the performance of strain 506 to its ability to produce cylindrospermopsins. The emphasis on a strain-specific light adaptation/acclimation is crucial to our understanding of how different light conditions (both quantity and quality) can trigger the occurrence of different C. raciborskii strains and control their competition and/or dominance in natural ecosystems.
The impacts of a high CO₂ environment on a bicarbonate user: the cyanobacterium Cylindrospermopsis raciborskii
Water research, 2012
The potentially toxic cyanobacterium Cylindrospermopsis raciborskii (Wołoszyńska) Seenya et Subba... more The potentially toxic cyanobacterium Cylindrospermopsis raciborskii (Wołoszyńska) Seenya et Subba Raju, originally described as a tropical-subtropical species, is increasingly found in temperate regions and its range is expanding. Climate change is hypothesised to be a factor in this expansion. We studied the effects of dissolved inorganic carbon (DIC) and pH on growth and photosynthesis of this species. We prepared six treatments in a continuous culture (turbidostat) grown at high light, two at low light, and eight in batch cultures grown under low light, by manipulating pH, HCO(3)(-) and CO(2) to assess the effect, if any, of these parameters on the growth rate, inorganic carbon acquisition and photosynthetic parameters of C. raciborskii. When the turbidostats were grown at 100 μmol photons (PAR) m(-2) s(-1), HCO(3)(-) concentration and pH had a positive effect on growth rate; the specific growth rate in 6 mM HCO(3)(-), for example, was twice what it was in 0.6 mM HCO(3)(-) (0.84 ...
Raman acoustic levitation spectroscopy (RALS) of living cells: Applications to malaria diagnosis and phytoplankton research
The impacts of a high CO< sub> 2 environment on a bicarbonate user; the cyanobacterium< i> Cylindrospermopsis raciborskii
... 2. Methods. 2.1. Culture. The strain of C. raciborskii used in this study was originally isol... more ... 2. Methods. 2.1. Culture. The strain of C. raciborskii used in this study was originally isolated from Lake Samsonvale (North Pine Dam), near Brisbane in south-east Queensland, Australia, in 1997 by Dr Glenn McGreggor. ... The method of Cassar et al. ...
Inorganic carbon acquisition by eight species ofCaulerpa (Caulerpaceae, Chlorophyta)
Phycologia, 2006
... Karen Kevekordes 1 , Daryl Holland 1 , Norbert HÄubner 1 , Sommer Jenkins 1 , Rebecca Koss 1 ... more ... Karen Kevekordes 1 , Daryl Holland 1 , Norbert HÄubner 1 , Sommer Jenkins 1 , Rebecca Koss 1 , Simon Roberts 1 , John A. Raven 2 , Charles M. Scrimgeour 3 , Kirsten Shelly 1 ... Badger, MR , JT Andrews , SM Whitney , M. Ludwig , DC Yellowlees , W. Leggat , and GD Price . ...
Analytical Chemistry, 2005
- Beardall, J.; Berman, T.; Heraud, P.; Kadiri, M.; Light, B.; Patterson, G.; Roberts, S.; Sahan... more 1) Beardall, J.; Berman, T.; Heraud, P.; Kadiri, M.; Light, B.; Patterson, G.; Roberts, S.; Sahan, E.; Schulzberger, B.; Urlinger, U.; Wood, B. R.
Inorganic carbon acquisition by eight species ofCaulerpa (Caulerpaceae, Chlorophyta
Phycologia, 2006
... Karen Kevekordes 1 , Daryl Holland 1 , Norbert HÄubner 1 , Sommer Jenkins 1 , Rebecca Koss 1 ... more ... Karen Kevekordes 1 , Daryl Holland 1 , Norbert HÄubner 1 , Sommer Jenkins 1 , Rebecca Koss 1 , Simon Roberts 1 , John A. Raven 2 , Charles M. Scrimgeour 3 , Kirsten Shelly 1 ... Badger, MR , JT Andrews , SM Whitney , M. Ludwig , DC Yellowlees , W. Leggat , and GD Price . ...
CO2 -concentrating mechanisms in three southern hemisphere strains of Emiliania huxleyi
Journal of phycology, 2013
Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence... more Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence the way phytoplankton acquire inorganic carbon. All phytoplankton rely on ribulose-bisphosphate carboxylase oxygenase (RUBISCO) for assimilation of inorganic carbon in photosynthesis, but this enzyme is inefficient at present day CO2 levels. Many algae have developed a range of energy demanding mechanisms, referred to as carbon concentrating mechanisms (CCMs), which increase the efficiency of carbon acquisition. We investigated CCM activity in three southern hemisphere strains of the coccolithophorid Emiliania huxleyi W. W. Hay & H. P. Mohler. Both calcifying and non-calcifying strains showed strong CCM activity, with HCO3 (-) as a preferred source of photosynthetic carbon in the non-calcifying strain, but a higher preference for CO2 in the calcifying strains. All three strains were characterized by the presence of pyrenoids, external carbonic anhydrase (CA) and high affinity for CO2 in...
Photosynthetic characteristics of two Cylindrospermopsis raciborskii strains differing in their toxicity
Journal of phycology, 2014
We studied the growth and photosynthetic characteristics of a toxic (CS506) and a nontoxic strain... more We studied the growth and photosynthetic characteristics of a toxic (CS506) and a nontoxic strain (CS509) of the bloom-forming cyanobacterium Cylindrospermopsis raciborskii grown under identical experimental conditions. When exposed to light-saturating growth conditions (100 μmol photons · m(-2) · s(-1) ), values for maximal photosynthetic capacity (Pmax ) and maximum quantum yield (Fv /Fm ) indicated that both strains had an equal ability to process captured photons and deliver them to PSII reaction centers. However, CS506 grew faster than CS509. This was consistent with its higher light requirement for saturation of photosynthesis (Ik ). Greater shade tolerance of CS509 was indicated by its higher ability to harvest light (α), lower photosynthetic light compensation point (Ic ), and higher chlorophyll a to biovolume ratio. Strain-specific differences were found in relation to non-photochemical quenching, effective absorption cross-sectional area of PSIIα-centers (σPSIIα), and the...
Nutrient induced fluorescence transients (NIFTs) provide a rapid measure of P and C (co-)limitation in a green alga
European Journal of Phycology, 2015
Harmful Algae, 2015
Cylindrospermopsis raciborskii is a toxic cyanobacterium which is responsible for the formation o... more Cylindrospermopsis raciborskii is a toxic cyanobacterium which is responsible for the formation of Harmful Algal Blooms (HABs) and it is commonly described to prefer low light conditions. To elucidate the mechanisms that makes this species successful in such environments, we studied the physiological characteristics of C. raciborskii (strain NPD) exposed to both saturating (80 mmol photons m À2 s À1 ) and suboptimal (10 mmol photons m À2 s À1 ) light intensities. When exposed to the low light of 10 mmol photons m À2 s À1 , C. raciborskii showed a slower cell division rate (m c ), lower respiration rate (R d ) and higher cell quotas of Chl a and phycocyanin. However, no differences in the cellular light harvesting efficiency (a) and maximal photosynthetic rate (P max ) were observed. Under low light, the unchanged photosynthesis was associated with both functional maintenance of the photosynthetic machinery and a larger cross-sectional area of PSIIa-centres (sPSIIa). In relation to the literature, our results indicate that C. raciborskii NPD responds to low light by changing the size of the light harvesting antenna. Ecologically, the physiological acclimations observed suggest that C. raciborskii NPD can perform well in environments where light intensity is low and relatively stable, as might occur during the final stages of HABs. ß
Photosynthesis research, 2014
The extremophilic green microalga Chlamydomonas acidophila grows in very acidic waters (pH 2.3-3.... more The extremophilic green microalga Chlamydomonas acidophila grows in very acidic waters (pH 2.3-3.4), where CO2 is the sole inorganic carbon source. Previous work has revealed that the species can accumulate inorganic carbon (Ci) and exhibits high affinity CO2 utilization under low-CO2 (air-equilibrium) conditions, similar to organisms with an active CO2 concentrating mechanism (CCM), whereas both processes are down-regulated under high CO2 (4.5 % CO2) conditions. Responses of this species to phosphorus (Pi)-limited conditions suggested a contrasting regulation of the CCM characteristics. Therefore, we measured external carbonic anhydrase (CAext) activities and protein expression (CAH1), the internal pH, Ci accumulation, and CO2-utilization in cells adapted to high or low CO2 under Pi-replete and Pi-limited conditions. Results reveal that C. acidophila expressed CAext activity and expressed a protein cross-reacting with CAH1 (the CAext from Chlamydomonas reinhardtii). Although the fu...
High CO2, UV, and carbon partitioning in Thalassiosira pseudonana
The interactive effects of uv radiation and enhanced CO2 concentrations on aquatic photoautotrophs
Understanding the effects of global climate change on the algae that form the basis of most aquat... more Understanding the effects of global climate change on the algae that form the basis of most aquatic food chains is of paramount importance in our ability to make informed decisions about the future of production systems, marine ecosystems, and the global carbon cycle. Despite the Montreal Protocol to restrict the release of harmful chlorofluorocarbons into the atmosphere, ozone levels have not recovered at all latitudes, and in some regions levels of UVB are still rising due to interactions with phenomena related to climate change. However, the effects of UV radiation may be modulated by other environmental changes. In this review, we discuss how factors such as elevated CO 2 and ocean acidification, increasing temperature, and reduced nutrient supply associated with enhanced stratification can interact with UV radiation to affect algal physiological performance and growth. For instance, nutrient limitation enhances UV-induced inhibition due to the reduced capacity of algae to screen out UVB and/or impairment of their capacity to repair damage. Higher temperatures tend to promote repair more than photochemical damage so result in a net reduction of UV inhibition. Elevated CO 2 and ocean acidification has complex interactions with UV radiation, with mixed net outcomes for algal productivity. Differential effects of UVA and UVB have been shown to depend on their irradiance levels; while moderate levels of UVA stimulate growth and photosynthesis of some algae, UVB almost always results in harm to marine primary producers.
Photosynthetic characteristics of two Cylindrospermopsis raciborskii strains differing in their toxicity
Marine microbes in the Plastic Age
Microbiology Australia, 2014
ABSTRACT We are living in the ‘Plastic Age’, but unfortunately our non-human relatives with whom ... more ABSTRACT We are living in the ‘Plastic Age’, but unfortunately our non-human relatives with whom we share our planet are not adapted to cope with the thousands of tons of plastic waste entering rivers, seas and oceans each year. Plastic poses both physical and chemical threats to aquatic life. It leads to damage or death of animals following plastic entanglement or ingestion and/or can lead to bioaccumulation of co-pollutants absorbed on plastic surfaces. Once ingested, co-pollutants can be absorbed into tissues and accumulated in the food chain. As nature’s biodegraders and recyclers, microorganisms may play a role in mitigating the impact of our disposable plastic lifestyle, or alternatively, plastic may serve as a vector for transport of pathogenic microorganisms into marine fauna. Here, we review current understanding of the microbiology of marine plastics and highlight future challenges for this emerging research discipline.
Phycologia, 2013
2013. Impacts of nitrogen limitation on the sinking rate of the coccolithophorid Emiliania huxley... more 2013. Impacts of nitrogen limitation on the sinking rate of the coccolithophorid Emiliania huxleyi (Prymnesiophyceae). Phycologia 52: 288-294.
Journal of Plant Physiology, 2014
We studied the physiological acclimation of growth, photosynthesis and CO 2 -concentrating mechan... more We studied the physiological acclimation of growth, photosynthesis and CO 2 -concentrating mechanism (CCM) in Cylindrospermopsis raciborskii exposed to low (present day; L-CO 2 ) and high (1300 ppm; H-CO 2 ) pCO 2 . Results showed that under H-CO 2 the cell specific division rate ( c ) was higher and the CO 2and light-saturated photosynthetic rates (V max and P max ) doubled. The cells' photosynthetic affinity for CO 2 (K 0.5 CO 2 ) was halved compared to L-CO 2 cultures. However, no significant differences were found in dark respiration rates (R d ), pigment composition and light harvesting efficiency (˛). In H-CO 2 cells, non-photochemical quenching (NPQ), associated with state transitions of the electron transport chain (ETC), was negligible. Simultaneously, a reorganisation of PSII features including antenna connectivity (J con PSII␣), heterogeneity (PSII␣/) and effective absorption cross sectional area (PSII␣/) was observed. In relation to different activities of the CCM, our findings suggest that for cells grown under H-CO 2 : (1) there is down-regulation of CCM activity; (2) the ability of cells to use the harvested light energy is altered; (3) the occurrence of state transitions is likely to be associated with changes of electron flow (cyclic vs linear) through the ETC; (4) changes in PSII characteristics are important in regulating state transitions.
CO 2 -concentrating mechanisms in three southern hemisphere strains of Emiliania huxleyi
Journal of Phycology, 2013
Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence... more Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence the way phytoplankton acquire inorganic carbon. All phytoplankton rely on ribulose-bisphosphate carboxylase oxygenase (RUBISCO) for assimilation of inorganic carbon in photosynthesis, but this enzyme is inefficient at present day CO2 levels. Many algae have developed a range of energy demanding mechanisms, referred to as carbon concentrating mechanisms (CCMs), which increase the efficiency of carbon acquisition. We investigated CCM activity in three southern hemisphere strains of the coccolithophorid Emiliania huxleyi W. W. Hay & H. P. Mohler. Both calcifying and non-calcifying strains showed strong CCM activity, with HCO3 (-) as a preferred source of photosynthetic carbon in the non-calcifying strain, but a higher preference for CO2 in the calcifying strains. All three strains were characterized by the presence of pyrenoids, external carbonic anhydrase (CA) and high affinity for CO2 in photosynthesis, indicative of active CCMs. We postulate that under higher CO2 levels cocco-lithophorids will be able to down-regulate their CCMs, and re-direct some of the metabolic energy to processes such as calcification. Due to the expected rise in CO2 levels, photosynthesis in calcifying strains is expected to benefit most, due to their use of CO2 for carbon uptake. The non-calcifying strain, on the other hand, will experience only a 10% increase in HCO3 (-) , thus making it less responsive to changes in carbonate chemistry of water.
Photosynthetic characteristics of two Cylindrospermopsis raciborskii strains differing in their toxicity
Journal of Phycology, 2014
We studied the growth and photosynthetic characteristics of a toxic (CS506) and a nontoxic strain... more We studied the growth and photosynthetic characteristics of a toxic (CS506) and a nontoxic strain (CS509) of the bloom-forming cyanobacterium Cylindrospermopsis raciborskii grown under identical experimental conditions. When exposed to light-saturating growth conditions (100 μmol photons · m(-2) · s(-1) ), values for maximal photosynthetic capacity (Pmax ) and maximum quantum yield (Fv /Fm ) indicated that both strains had an equal ability to process captured photons and deliver them to PSII reaction centers. However, CS506 grew faster than CS509. This was consistent with its higher light requirement for saturation of photosynthesis (Ik ). Greater shade tolerance of CS509 was indicated by its higher ability to harvest light (α), lower photosynthetic light compensation point (Ic ), and higher chlorophyll a to biovolume ratio. Strain-specific differences were found in relation to non-photochemical quenching, effective absorption cross-sectional area of PSIIα-centers (σPSIIα), and the antenna connectivity parameter of PSIIα (Jcon PSIIα). These findings highlighted differences in the transfer of excitation from phycobilisome/PSII to PSI, on the dependence on different pigments for light harvesting and on the functioning of the PSII reaction centers between the two strains. The results of this study showed that both performance and composition of the photosynthetic apparatus are different between these strains, though with only two strains examined we cannot attribute the performance of strain 506 to its ability to produce cylindrospermopsins. The emphasis on a strain-specific light adaptation/acclimation is crucial to our understanding of how different light conditions (both quantity and quality) can trigger the occurrence of different C. raciborskii strains and control their competition and/or dominance in natural ecosystems.
The impacts of a high CO₂ environment on a bicarbonate user: the cyanobacterium Cylindrospermopsis raciborskii
Water research, 2012
The potentially toxic cyanobacterium Cylindrospermopsis raciborskii (Wołoszyńska) Seenya et Subba... more The potentially toxic cyanobacterium Cylindrospermopsis raciborskii (Wołoszyńska) Seenya et Subba Raju, originally described as a tropical-subtropical species, is increasingly found in temperate regions and its range is expanding. Climate change is hypothesised to be a factor in this expansion. We studied the effects of dissolved inorganic carbon (DIC) and pH on growth and photosynthesis of this species. We prepared six treatments in a continuous culture (turbidostat) grown at high light, two at low light, and eight in batch cultures grown under low light, by manipulating pH, HCO(3)(-) and CO(2) to assess the effect, if any, of these parameters on the growth rate, inorganic carbon acquisition and photosynthetic parameters of C. raciborskii. When the turbidostats were grown at 100 μmol photons (PAR) m(-2) s(-1), HCO(3)(-) concentration and pH had a positive effect on growth rate; the specific growth rate in 6 mM HCO(3)(-), for example, was twice what it was in 0.6 mM HCO(3)(-) (0.84 ...
Raman acoustic levitation spectroscopy (RALS) of living cells: Applications to malaria diagnosis and phytoplankton research
The impacts of a high CO< sub> 2 environment on a bicarbonate user; the cyanobacterium< i> Cylindrospermopsis raciborskii
... 2. Methods. 2.1. Culture. The strain of C. raciborskii used in this study was originally isol... more ... 2. Methods. 2.1. Culture. The strain of C. raciborskii used in this study was originally isolated from Lake Samsonvale (North Pine Dam), near Brisbane in south-east Queensland, Australia, in 1997 by Dr Glenn McGreggor. ... The method of Cassar et al. ...
Inorganic carbon acquisition by eight species ofCaulerpa (Caulerpaceae, Chlorophyta)
Phycologia, 2006
... Karen Kevekordes 1 , Daryl Holland 1 , Norbert HÄubner 1 , Sommer Jenkins 1 , Rebecca Koss 1 ... more ... Karen Kevekordes 1 , Daryl Holland 1 , Norbert HÄubner 1 , Sommer Jenkins 1 , Rebecca Koss 1 , Simon Roberts 1 , John A. Raven 2 , Charles M. Scrimgeour 3 , Kirsten Shelly 1 ... Badger, MR , JT Andrews , SM Whitney , M. Ludwig , DC Yellowlees , W. Leggat , and GD Price . ...
Analytical Chemistry, 2005
- Beardall, J.; Berman, T.; Heraud, P.; Kadiri, M.; Light, B.; Patterson, G.; Roberts, S.; Sahan... more 1) Beardall, J.; Berman, T.; Heraud, P.; Kadiri, M.; Light, B.; Patterson, G.; Roberts, S.; Sahan, E.; Schulzberger, B.; Urlinger, U.; Wood, B. R.
Inorganic carbon acquisition by eight species ofCaulerpa (Caulerpaceae, Chlorophyta
Phycologia, 2006
... Karen Kevekordes 1 , Daryl Holland 1 , Norbert HÄubner 1 , Sommer Jenkins 1 , Rebecca Koss 1 ... more ... Karen Kevekordes 1 , Daryl Holland 1 , Norbert HÄubner 1 , Sommer Jenkins 1 , Rebecca Koss 1 , Simon Roberts 1 , John A. Raven 2 , Charles M. Scrimgeour 3 , Kirsten Shelly 1 ... Badger, MR , JT Andrews , SM Whitney , M. Ludwig , DC Yellowlees , W. Leggat , and GD Price . ...